Telephone receiver



June 8 1926. 1,587,719

H. GERNSBACK TELEPHONE RECEIVER Filed Nov. 15, 1923 2 Sheets-Sheet 1 9 finoento'o HUGO GERNSBA CK June 8 1926. 1,587,719

H. GERNSBACK TELEPHONE RECEIVER Filed Nov. 15, 1923 2 Sheets-Sheet 2 H060 GER/V6BACK Patented June 8-, 1926.

HUGO GERNSBAGK, OF NEW YORK, N. Y.

TELEPHONE Rncnivnn.

Application filed November 15, 1923. Serial No. 674,808.

This invention relates to the construction of telephone receivers and the objects of the invention are to reduce the magnetic reluctance, prevent loss or dissipation of the magnetic energy, to apply the pull or actuating force directly to the center of the diaphragm so as to gain the maximum results and to effect this without distorting or damping the action of the diaphragm.

In the attainment of the foregoing and other desirable results a number of novel features of construction, combinations and relations of parts are employed as will be clear from the following specification, which is to be read in conjunction with the drawing accompanying and forming part of the same.

In the drawing, Figure 1 is a cross sectional view of a receiver constructed in accondance with and embodying the principles of this invention.

Figure 2 is a plan view of the same with the ear cap and diaphragm removed and a part of the coil broken away to show the seat for the magnet yoke formed in the bottom of the case.

' Figure 3 is a detached perspective View of the magnetic yoke.

Figures 4 and 5 are broken sectional and plan views of a modified construction in which the magnetic circuit is completed by engagement of the diaphragm with the end poles of the yoke and in which the center pole is of elongated instead of circular shape.

Figures 6', 7 and 8 are broken sectional views of other modifications.

The case 5 of the receiver which is shown as of the usual cup shape may be formed of aluminum or other non-magnetic material and is illustrated as having a tranverse seat or depression 6 extending across the bottom of the same. i

The permanent magnet is shown in the form of a single, one piece bar having its opposite ends bent to form pole pieces 8 extending substantially at right angles from the intermediate straight back portion 9.

The back of the magnet yoke seats in the transverse cavity in the bottom of the case and in the first form of the invention illustrated is of a length almost equal to the inside diameter of the case so as to bring the polar projections closely adjacent the inner wall of the case. In order that these pole pieces may fit the closer to the surrounding wall, they are shown in Figure 2 as curve on an arc approximating the curvature of such wall.

At the center of the magnet yoke there is secured a centrally disposed pole piece 10 which carries the magnet winding 11. In the first form of the invention, illustrated in Figures 1 to 3, the central pole is shown secured to the yoke and both secured within the case by a single fastening screw 12 entered through a hole 13 in the back of the case and extending freely through an opening 14 in the back of the yoke into a screwthreaded seat 15 in the end of the ma net core or pole piece 10. This screw is usual y made, of magnetic material so that the pole piece will not be reduced in magnetic cross section and the end of the pole piece and the back of the yoke are preferably faced off to provide a close abutting fit between these parts to prevent any loss of magnetic energy at this point. a

The end of the central pole which is opposed to the diaphragm 16 is usually cupped or formed with a cavity 17 at its center to equalize the pull on the diaphragm through substantially an area represented by the circular end of the pole instead of being concentrated at the center of this pole.

The diaphragm is shown as secured over the edge of the case by an ear cap 18 having a screwthreaded engagement 19 over the wall of the case and the magnet winding is shown as having insulated terminals 20, 21

carried out through the back of the case.

In the course'of manufacture and usually after the parts are assembled in the case the magnet system is permanently energized, the polar projections of the magnet'yoke being both made of the same sign and the central polar projection being made of the opposite sign. The side poles thus provide return magnetic paths for the magnetic flux developed at the central polar projection and an important feature of this is the location of the side poles close to the clamped peripheral portion of the diaphragm where these poles can have no damping effect upon the diaphragm. In this way the return magnetic paths are provided and full and free action of the diaphragm is secured without any objectionable retarding or damping effect.

To further reduce the magnetic reluctance, the air gaps in the return path may f be entirely eliminated as illustrated in Figures 4 to 8.

In the constructionshown in Figures 4 and 5 the polar projections of the yoke are extended and turned over at right angles and faced off in a lane with the edge of the cup or support or the diaphragm so as to be directly engaged by the fixed edge portion of the diaphragm. To provide the room for these lateral polar extensions 22, the adjacent wall of the case may be notched as indicated at 23.

This construction provides a complete metallic magnetic return, enabling the full ower to be exerted on the center of the 'aphragm. Also with this construction it will be seen that the magnet yoke is secured within the case by the diaphragm which in turn is held in place by the ear cap. With this construction therefore the securing screw at the back of the case may be eliminated provided the center pole is fixed to the yoke, as it is for instance in Figure 4 by constructing it with a screw stud extension 24 taking into a screw seat provided in the back of the yoke. This screw stud is actually shown as extended through the back of the case and as having a nut 25 applied thereto, but if desired, the magnet system may be held in place within the case entirely by the screw cap or diaphragm securing means.

It has been found that for certain pur-' poses, for instance, for loud speakers, better results are attained where the central or actuating pole is of noncircular form, as of the elongated shapeshown at -26 extending approximately the full width of the magnet 1 yoke.

In Figure 6 a full metallic return for the magnetic circuit is shown provided by extending narrow projections 27 at the outer edges of the end poles into contact with outer pleripheral portions of the diaphragm. This's ould be an intimate firm contact to prevent chattering of the diaphragm at these points. I

The full metallic return may also be pro vided by projections from the diaphragm. Thus in Figure 7 tongues 28 are shown partially severed from the edge of the diaphragm and'bent down soas to lie in engagement with the outer sides of the end p0 es.

In Figure 8 practically the same result is attained by unching integral ribs 29 from pole long the body of t e diaphragm inward from the edge thereof so as to fit in the aces between the end poles and surroun ing wall and in contact with such poles.

In lace of the screw fastenings heretofore escribed for securing the central polar projection, a rivet fastening may be employed, as indicated at 30 in Figure 6, by making the studgon the end of the central enough to extend out through the case'an there turning or heading it over theoutside of the case. x

In all these latter described forms of the invention where the ends of the magnet yoke are in actual engagement with the diaphragm, the full effect of the magnet winding is made available to actuate the diaphragm and consequently the receiver is more sensitive to weak signals and the volume of sound produced is greater.

What I claim is:

1. A telephone receiver comprising a case having a cavity extending across the bottom of the same, a magnet structure having a back portion seated in said cavity and thereby held against turning within the case, polar projections at the ends of such back portion standing closely adjacent the wall of the case, a pole piece seated on the back portion and a securing member extending from said pole iece past the back portion and out throug the case for securing the pole piece on the back portion and for fastening both the pole piece and the magnet structure within the case.

2. In a telephone receiver, a case, a magnet structure comprising a yoke bearing directly on the back of the case having polar projections at the ends of the same and an intermediate substantially centrally disposed polar projection. bearing directly on said yoke provided with a sc ew seat in one end and a securing screw extending through the case and into said screw seat for fastening the entire magnet structure within the case.

3. The structure of claim 2 in which the polar projections at the ends of the one piece magnet yoke are curved approximately on the arc of the inside of the case to thereby 4. In a telephone receiver a magnetic diaphragm held substantially immovable at its periphery, an actuating magnet having poles opposed to the substantially immovable peripheral portion of the diaphragm and a pole oplposed to the central portion of the diap ragm and having a centrally disposed cavity in the end face of the same directly opposed to the diaphragm but clear of engagement therewith.

5. In a telephone receiver, a case having a diametrically extending cavity in the bottom of the same, a magnet oke having a back portion seated and hel against turning in said cavity and a central polar projection and screw means engaged with said central polar projection for securing the magnet structure in the case.

6. A telephone receiver comprising a case having a cavity extending across the bottom of the same, 'a magnet structure having a back ortion seated in said cavity and thereby he d against turning in the case, polar projections at the ends of the thus seated and to secure the assembled magnet structure back portion, a central pole piece having a in fixed position within the case, a winding 10 screw seat in one end and bearing directly on the centralpole piece and terminals for upon the back portion, a screw of magnetic said winding mounted in the case at one side material entered from the outside of the case of the magnet seating cavity.

past the back portion and engaged in said ,In witness whereof, I have hereunto Set screw seat to provide a magnetic connection my hand this 9th day of November, 1923. between the pole piece and back portion HUGO GERNSBAGK. 

